VCE General Mathematics

## Types of data A **variable** is a characteristic that can differ from one person or object to the next, and the values it takes are the data. The first step in any analysis is to classify the variable, because the type decides which displays and summary statistics make sense. | Type | Subtype | What the values are | Example | |---|---|---|---| | Categorical | Nominal | Labels with no natural order | Type of home, eye colour, postcode | | Categorical | Ordinal | Labels that can be put in a meaningful order | Satisfaction (low, medium, high), school year | | Numerical | Discrete | Counts, which take separate values | Number of siblings, goals scored | | Numerical | Continuous | Measurements, which can take any value in an interval | Height, time, mass | Two points cause most of the mistakes. A number is not always a numerical variable: a postcode or a jersey number is a label, so it is nominal, and arithmetic on it means nothing. A category is ordinal when the order itself carries information, although the gaps between the categories are not measured, so the difference between "high" and "medium" is not known to equal the difference between "medium" and "low". Continuous data are usually recorded to a limited accuracy (a height to the nearest centimetre, say), but the variable is still continuous because it could in principle be measured more finely. ## Frequency tables The **frequency** of a category is the number of observations in it. A frequency table lists each…